1. Field of the Invention
This invention relates to hydroformylation processes. In one aspect the invention relates to the mitigation of fouling in hydroformylation processes while in another aspect, the invention relates to the mitigation of fouling in such processes by the addition of water.
2. Description of the Related Art
In the rhodium/bisphosphite-catalyzed hydroformylation of olefins, the bisphosphite ligand slowly and inexorably degrades to a number of byproducts. Some of these byproducts are acidic, and may be removed by contacting the reaction solution with an aqueous buffer (e.g. sodium phosphate). The resulting metal salts are appreciably soluble in water, and can be effectively removed from the organic phase. This extraction process is described in WO 97/20794.
Following contact with the aqueous buffer, the organic phase is returned to the reactor system. Although the two phases are immiscible, some gradual entrainment of aqueous buffer into the reactor may occur. Upset conditions may also cause episodic, inadvertent carryover of aqueous buffer into the reaction process. The result is the formation of acid metal salts in the reaction system.
Although the acid metal salts are soluble in water, they are sparingly soluble in the organic matrix. Surprisingly they may also swell and/or become sticky when the water level of the organic matrix is 0.1 percent by weight or greater. This gelatinous, sticky material can cling to cool surfaces, e.g., heat exchangers, control valves, distributors, etc., and, in turn, reduce their operating efficiency.